1. Field of the Invention
The present invention relates to a technology for printing images by jetting ink droplets from each of a plurality of nozzles to record dots on the surface of a printing medium, and particularly to a printing technology utilizing dot dropout inspection that inspects whether or not ink droplets are jetted from the nozzles.
2. Discussion of the Background
An inkjet printer prints images by jetting ink droplets from a plurality of nozzles. The print head of an inkjet printer is equipped with a large number of nozzles. Due to an increase in ink viscosity and/or bubble entrainment and the like, some of the nozzles may clog and become incapable of jetting ink droplets. Nozzle clogging becomes a cause of image quality degradation by causing dot dropout within the image.
The background way of inspecting for nozzle clogging is for the user to print a special test pattern on printing paper before starting a printing job and to then examine the printed test pattern visually. In this description, a xe2x80x9cprinting jobxe2x80x9d means the entire printing operation performed in response to a single user instruction.
Since inspection has been conducted only before the printing job, it has been impossible to obtain the desired image quality when dot dropout occurred in the course of the printing operation.
Accordingly, one object of the present invention is to provide novel technology enabling mitigation of image quality degradation even when dot dropout occurs in the course of a printing operation.
A further object of the present invention is to overcome the above-noted problems of the background art.
In order to attain at least part of the above objects of the present invention, an inspection is conducted to inspect the presence/absence of jetting of ink droplets from nozzles subject to inspection, during a printing operation to determine whether each nozzle subject to inspection is an operative nozzle capable of jetting ink droplets or an inoperative nozzle incapable of jetting ink droplets. In this arrangement, dots are made up using another nozzle that is operative when an inoperative nozzle is detected or by cleaning the inoperative nozzle and then using the cleaned nozzle, and thereby degradation of image quality by dot dropout occurring in the course of the printing operation can be mitigated.
The inspection is preferably conducted at every main scan during ordinary printing operation which is performed when no inoperative nozzle is present. In this arrangement, any inoperative nozzle that occurs can be detected in a short time.
Cleaning may be conducted with respect to at least the inoperative nozzle when the inspection detects the inoperative nozzle, and the make-up operation may be conducted when operation of the inoperative nozzle is not restored by a prescribed number of cleanings.
Further, when operation of the inoperative nozzle is restored within the prescribed number of cleanings, the make-up operation may be conducted for recording dots that should have been recorded by the inoperative nozzle using the restored active nozzle. In this arrangement, since dots that were not recorded can be recorded by the nozzle that should have been in charge of recording the dots, dot make-up can be readily conducted.
The make-up operation may be an operation of recording only dots on a main scanning line that should have been recorded by the inoperative nozzle using the other active nozzle or the restored active nozzle. In this arrangement, it is possible to prevent degradation of image quality that would occur if dots in other normally printed main scan lines should be overstruck during the make-up operation.
It is preferable that, in the make-up operation, i) before the make-up operation, a sub-scan feed of a transient first feed amount is conducted in order to position the active nozzle on the main scanning line including the dots that should have been recorded by the inoperative nozzle; and ii) after the make-up operation, a sub-scan feed of a transient second feed amount is conducted in order to position the plurality of nozzles at a nozzle position of the next main scan of the ordinary printing operation. In this arrangement, a make-up operation for eliminating dot dropout can be easily conducted without substantially changing the ordinary printing operation.
According to another aspect of the present invention, an inspection for the presence/absence of jetting of ink droplets from nozzles subject to inspection is conducted, during a printing operation, to determine whether each nozzle subject to inspection is an operative nozzle capable of jetting ink droplets or an inoperative nozzle incapable of jetting ink droplets, and when an inoperative nozzle is detected by the inspection, processing after the inspection is conducted in accordance with a processing procedure selected by a user. In this arrangement, a processing procedure suitable for the circumstances can be selected based on the user""s judgment.
The present invention can be implemented in various modes including, for example, a printing method and device, a computer program for realizing the functions of the method or device, a storage medium recorded with the computer program, and data signals including the computer program embodied in a carrier wave.